This invention relates to a valve assemlby for single-lever actuated mixer taps of the type having a flow controlling slide provided with peripheral recesses.
Valve assemblies with slides,which, instead of peripheral recesses have holes in the body of the slide, are not of interest for this invention.
U.S. Pat. No. 3,965,935 discloses a valve assembly for single-lever mixer taps which comprises essentially a bearing supporting a spherical body in sealed relationship, wherefrom there extend, at the top, an actuating lever accessible from the outside and, at the bottom, a pivot for connection to a ceramic disk slide accommodated in the mixing chamber and provided with peripheral recesses.
Said ceramic disk is movable over a pair of tubular seats of ceramics, respectively connected to the hot water and cold water supply conduits, which are urged elastically against the ceramic disk, thereby a valve assembly is formed.
For the desired delivery of water, along the periphery of the ceramic disk, there are provided triangular peripheral recesses which, by shifting the disk position, can be brought into alignment with orifices defined in the tubular seats, to thus obtain a desired delivery of water. It will be appreciated that the sealing contact between the disk and the tubular seats occurs on the annular edge or rim of the orifices of the tubular seats and the disk face in contact therewith.
In the extreme positions, one of which is represented by the delivery of just hot water or cold water, the ceramic disk would only overlie a small part of the annular edge of respective tubular seat orifice (see e.g. FIG. 4 of the cited U.S. Patent), so that it may happen that, owing to the unavoidable clearance, or play, of the tubular seat in its retaining guide cavity, the tubular seat tends to cock from its vertical axis perpendicular to the plane of lay of the ceramic disk. Consequently, during the subsequent closing phase, the corner edge of the triangular recess defined by the ceramic disk would in practice strike against the inward peripheral edge of the orifice of the top of the tubular seat, which being inclined because of the reason explained above, is at a higher level than the plane of lay of the ceramic disk bottom face. Repeated striking of the corner edge against the inward portion of the ceramic seat top edge results with time in a slightly abraded top edge of the tubular seat which,after a certain period of use, impairs the mating contact of the ceramic disk bottom surface and top edge of the tubular seat, so that an area is thus created where tightness deteriorates, which results in a dripping tap and the necessity of replacing the valve assembly.